In wireless communications, an amplitude of radio frequency data, that is, a radio frequency signal, received by a radio frequency receiver changes dramatically. To ensure performance of the radio frequency receiver, the radio frequency receiver needs to support a large dynamic receive range. To reduce bit width and reduce costs, it is required to adjust, in an automatic gain control (AGC) manner, the radio frequency data according to the amplitude of the received radio frequency data, so as to adjust the amplitude of the received radio frequency data to a proper range, and then perform quantizing using an analog to digital converter (ADC), so as to achieve a purpose of reducing bit width and reducing costs.
Referring to FIG. 1, FIG. 1 is a schematic structural diagram of a radio frequency receiver in the prior art. As shown in FIG. 1, an existing radio frequency receiver 10 includes a radio frequency component 11, an analog to digital converter 12, a base band filter 13, an AGC gain controller 14, an average power calculator 15, and a Fourier transformer 16. Further referring to FIG. 2, FIG. 2 is a schematic diagram of an AGC calculation period. As shown in FIG. 2, the AGC calculation period is 5 milliseconds (ms), which includes five subframes whose duration is 1 ms. The radio frequency receiver 10 in the prior art generally calculates an actual average power intensity in a period of time, for example, a calculation period, and further uses a difference between the actual average power intensity and a target average power intensity as a gain value of radio frequency data in a next calculation period, to perform an adjustment on an actual average power intensity of the radio frequency data in the next calculation period.
Calculation on the actual average power intensity are performed in the following manners:
Manner 1: The AGC gain controller 14 calculates, using the average power calculator 15, an actual average power intensity of the digital data before being filtered by the base band filter 13, and then adjusts a gain of the radio frequency component 11 on radio frequency data according to a calculation result, so as to ensure that components, such as the analog to digital converter 12, are unsaturated.
Manner 2: The average power calculator 15 is disposed at an output end of the base band filter 13 (refer to the dashed line in the figure), and the AGC gain controller 14 calculates, using the average power calculator 15, an actual average power intensity of digital data after being filtered by the base band filter 13, and then adjusts a gain of the radio frequency component 11 on radio frequency data, so as to ensure that a signal-to-noise ratio of radio frequency data that is quantized by an ADC is high.
Manner 3: The average power calculator 15 is disposed at an output end of the Fourier transformer 16 (refer to the dashed line in the figure), and the AGC gain controller 14 calculates an average power intensity of a cell reference signal resource element, which is energy that carries a cell-specific reference signal resource element (CRS RE) or an average power intensity of an effective subcarrier signal using the average power calculator 15, and then adjusts a gain of the radio frequency component 11 on radio frequency data according to a calculation result, so as to prevent dynamic changes, of signal time-domain power, that are brought by different scheduling in different periods.
In an actual application, in a coordinated multipoint (CoMP) scenario, transmission point (TP) switching causes a relatively large sudden change in wanted signal power (that is, actual average power) between subframes. In a heterogeneous network (HeNet) scenario, interference coordination of a macro base station or a micro base station also causes a relatively large sudden change in a level of interference between subframes. If calculating methods in the foregoing manners are used, it is required to use a calculation result of a previous calculation period in a next calculation period. If there is a great change in wanted signal power (or interference power) in a calculation period, a difference of the previous calculation period is directly used to adjust an actual average power intensity of the next calculation period. On one hand, a large difference adjustment easily leads to a mistake; on the other hand, an actual average power intensity in the previous calculation period cannot well reflect an actual average power intensity in the next calculation period due to an overlong calculation period. Therefore, an adjustment result may have a large deviation. For example, if an actual average power intensity of radio frequency data in a previous calculation period is 10 decibel (dB), and a target average power intensity is 20 dB, a gain value in a next calculation period is 10 dB. If there is a large difference between the actual average power intensity in the next calculation period and the actual average power intensity in the previous calculation period, for example, the actual average power intensity of the next calculation period is 20 dB, an improper adjustment occurs when the actual average power intensity in the next calculation period is adjusted by directly using the 10 dB gain value calculated in the previous calculation period. When the actual average power value in the next calculation period is much less than that in the previous calculation period, for example, the actual average power value in the next calculation period is 5 dB, the adjustment result is also improper. That is, an adjustment on a gain of radio frequency data in the next calculation period by directly using the difference calculated in the previous calculation period is a rough adjustment, an adjustment result does not meet a requirement, and it is required to perform multiple adjustments; therefore, saturation distortion of the radio frequency component is easily caused, or power of the radio frequency data is too low to reach a signal-to-noise ratio required for demodulation, thereby causing a higher bit error on the radio frequency receiver 10, and reducing a throughput.